How can I remove this exterior vent in my attic? I have wasps living in there because the netting behind this vent has deteriorated somehow. I have new netting to staple up but I can't for the life of me figure out how to get this vent off from the outside of the house.

Is there such a thing as a replacement that installs from the outside? I could tear this one out fairly easily. Getting to this from inside the attic is a huge hassle, not to mention I think there's a giant wasp nest just inside this vent.

The vent has a flashing that's under the siding a few inches. It's used to nail it to the wall and prevent water from getting in behind it. You would need to remove the siding as it butts up to the vent over the flashing.
If it's vinyl siding you may be able to pull it off, remove the vent, replace the screen and reinstall. Same goes for aluminum siding but it's much less forgiving if you bend or crease it when removing.
I would reconsider crawling into the attic, if possible, with a piece of screen, a staple gun, and a can of wasp spray.

Ok, thanks for your help. I'll climb up in there and blast 'em good while it's still cold. I think Red Wasps (Hornets, actually) are slow in the cold. If it's a giant nest perhaps I'll post a photo of their carcasses and the hole I put in my ceiling when I'm scrambling out of there while being stung, LOL

It’s really pretty easy to unsnap the siding and take it off if you want to go at it from the outside. They sell a hook tool you jam up under the siding and unsnap it and most of the time you can pop it on and off the nails to replace it. There are a bunch of videos on line showing how to do this. I would not take it down in super cold conditions as it gets brittle. If you have an attic that’s easy to get in and out of then I would take a look at doing it that way just adding a new screen on the inside.

Oh man, you guys are great. This vent is on the far end of my ranch-style house from the attic access and then I'd have to shimmy down between two joists to get to this vent from the inside. It's a pretty big hassle, not to mention fighting off hornets while I'm straddling two joists with my staple gun. I've got some bug bombs I'm going to toss in there this weekend regardless of how I get to this, either from the inside or outside.

Anyhow, I l watched video on how to use that siding tool. I assume the siding is cut in a circular pattern underneath this vent's trim piece.

Are you suggesting that the best way to get to this from the outside of the house is to completely remove these short siding pieces, then I'll be able to get to the flashing around the vent so I can remove the nails/screws to remove the vent? I assume I'll need to scrape away and replace some caulking, etc as well.